Conventional organopolysiloxane compositions which cure at room temperature (RT) into rubber-like elastomers include one-pack RT curable organopolysiloxane compositions in which cure reaction takes place upon contact with airborne moisture. The one-pack organopolysiloxane compositions are widely used as elastomeric adhesives and coating materials in the electrical and electronic industry, building sealants, and the like because these compositions dispense with cumbersome steps of weighing and mixing base polymer, crosslinker and catalyst immediately before use, and are thus devoid of any compounding errors. In addition, they generally have excellent adhesion to a wide variety of substrates even in the absence of primers. The one-pack RT curable organopolysiloxane compositions are often classified in terms of the compound which is released from the composition upon contact with airborne moisture, typically into deacetic acid, deoximation, deamidation, dehydroxylamination, deacetonation and dealcoholization types. Of these, organopolysiloxane compositions of the dealcoholization type, which cure while releasing alcohol, are preferred because they give off less odors, and are non-corrosive to metals such as cupper and iron, and good in self-adhesion (as-cured adhesion to various substrates in the absence of primers) and durable adhesion.
One-pack organopolysiloxane compositions of the dealcoholization type display excellent properties as described above for a brief time after preparation, but has the drawback of storage instability. For example, some compositions lose their initial properties with the lapse of time during storage. After storage in a high temperature environment in excess of 50° C., as often found during field storage under direct sunlight or storage in containers during transport, even for a relatively short period of time, there arise problems like failure to maintain the initial properties and under-cure.
One-pack organopolysiloxane compositions of the dealcoholization type are known from the past. For example, JP-B S39-27643 discloses a composition comprising a hydroxyl end-blocked organopolysiloxane, alkoxysilane, and titanium compound. JP-A S55-43119 discloses a composition comprising an alkoxysiloxy end-blocked organopolysiloxane, alkoxysilane, and alkoxytitanium. However, these compositions have problems that they become storage unstable when calcium carbonate is compounded for imparting good physical properties as sealants; they fail to display the desired properties after long-term storage; and they lose curability after storage in a high temperature environment above 50° C. JP-B H07-39547 proposes a composition having storage stability in a hermetically sealed package. Since the composition proposed essentially comprises an organopolysiloxane polymer terminally modified with an alkoxysilylalkylene radical, the preparation of the polymer adds to the industrial cost. Recently, JP-A H02-38309 and JP-A 2003-176411 disclose compositions using fatty acid ester-treated calcium carbonate, which are insufficient in storage stability at high temperature above 50° C. In addition, since the fatty acid ester-treated calcium carbonate is a special filler, compositions with heavy loadings of the filler become expensive.